Use of a nonionic detergent (Triton WR 1339) in healthy cats to assess hepatic secretion of triglyceride.

OBJECTIVE: To determine whether a nonionic detergent (Triton WR 1339) can be used in cats to assess hepatic secretion of triglyceride. ANIMALS: 28 healthy cats. PROCEDURE: Triton WR 1339 was administered IV according to the following schedule: 5, 50, 150, and 250 mg/kg of body weight. Control cats did not receive an injection or received 0.9% NaCl or PBS solutions at the same osmolarity and volume as the 250 mg/kg group. Blood samples were collected throughout the 48-hour period after administration for determination of triglyceride and cholesterol concentrations and for RBC morphology and osmotic fragility studies. RESULTS: Administration of Triton WR 1339 at 150 and 250 mg/kg caused profound hypertriglyceridemia. Triglyceride concentrations increased in a curvilinear fashion for the first 2 hours and remained increased for approximately 24 hours. Area under the time-concentration curve for triglyceride at 5 hours differed significantly among groups. At 12 and 24 hours, cholesterol was significantly higher in cats receiving 250 mg/kg. The most dramatic changes in osmotic fragility and RBC morphology were in cats receiving 250 mg/kg; 1 of these cats developed severe icterus and died 5 days later. Feeding rice and casein before administering Triton WR 1339 at 150 mg/kg did not appear to affect the hypertriglyceridemia response. CONCLUSIONS AND CLINICAL RELEVANCE: Triton WR 1339 can be administered IV to cats at a rate of 150 mg/kg to assess hepatic triglyceride secretion, although some cats may have increased RBC osmotic fragility. Higher dosages caused substantial adverse effects, whereas lower dosages did not alter plasma triglyceride concentration.

Effect of dietary n-6-to-n-3 fatty acid ratio on complete blood and total white blood cell counts, and T-cell subpopulations in aged dogs.

OBJECTIVE: To determine effect of diets with variable n-6-to-n-3 fatty acid (FA) ratio on CD4+ and CD8+ T-lymphocyte subpopulations, and on results of routine laboratory analyses (CBC and total WBC count, serum biochemical analyses, and urinalysis). ANIMALS: 20 healthy, aged (9.5 to 11.5 years old) female Beagles. PROCEDURE: Dogs were fed 1 of 3 diets that contained 6% fat by weight but differed in amounts of n-6 and n-3 FA. For 11 weeks, 6 dogs were fed a low concentration of n-3 FA (ratio, 31:1), 7 were fed a medium concentration (5.4:1), and 7 were fed a high concentration (1.4:1). Preprandial blood and urine samples were collected before beginning the study and at 8 weeks for evaluation of laboratory variables. Before and at 3, 6, and 8 weeks during the study, blood was drawn for total WBC and lymphocyte counts and for characterization of T-cell subpopulations. At 8 and 10 weeks, dogs were vaccinated with keyhole limpet hemocyanin suspension. Blood was drawn 4 days after each vaccination, and lymphocytes were isolated for flow cytometry. Effects of diet and vaccination on each variable were determined. RESULTS: After vaccination, total lymphocyte count increased and CD4+ T lymphocyte count and the CD4(+)-to-CD8+ ratio decreased in dogs consuming the diet with n-6-to-n-3 FA ratio of 1.4:1. CONCLUSION: Feeding a diet with n-6-to-n-3 FA ratio of 1.4:1 had significant effects on CD4+ T lymphocytes in healthy, aged Beagles after vaccination.

The ratio of dietary (n-6) to (n-3) fatty acids influences immune system function, eicosanoid metabolism, lipid peroxidation and vitamin E status in aged dogs.

We studied the effects of feeding experimental diets containing (n-6) to (n-3) fatty acid ratios of 31:1, 5.4:1, and 1.4:1 to 20 healthy female geriatric Beagles (9.5-11.5 y) for 8-12 wk on various indices of the immune response. Compared with the 31:1 diet, consumption of the 5.4:1 and 1.4:1 diets significantly increased (n-3) fatty acids in plasma (2.17 +/- 0.64, 9.05 +/- 0.64, 17.46 +/- 0.64 g/100 g fatty acids, respectively, P < 0.0001). Although supplementation with (n-3) fatty acids did not significantly alter the humoral immune response to keyhole limpet hemocyanin (KLH), it significantly suppressed the cell-mediated immune response based on results of a delayed-type hypersensitivity (DTH) skin test. The DTH response after intradermal injection of KLH at 24 h was significantly lower in the group consuming the 1.4:1 diet compared with the group consuming the 5.4:1 (P = 0.02) or the 31:1 diets (P = 0.04), and remained significantly suppressed at 48 h in the group fed 1.4:1 relative to the group fed 31:1. After consumption of the 1.4:1 diet, stimulated mononuclear cells produced 52% less prostaglandin E2 (PGE2) than those from dogs fed the 31:1 diet (224 +/- 74 and 451 +/- 71 pmol/L, respectively, P = 0.04). Plasma concentration of alpha-tocopherol was 20% lower in dogs fed the 1.4:1 diet compared with those fed the 31:1 diet (P = 0.04), and lipid peroxidation was greater in both plasma (P = 0.03) and urine (P = 0.002). These data suggest that although a ratio of dietary (n-6) to (n-3) fatty acids of 1.4:1 depresses the cell-mediated immune response and PGE2 production, it increases lipid peroxidation and lowers vitamin E concentration.

Serogrouping of Bacteroides nodosus isolates from 62 sources in the United States.

Bacteroides nodosus isolates from 62 sources in the United States were obtained from sheep with infectious foot diseases. Serotypic analysis of these isolates revealed 21 serotypes (designated I-XXI). These serotypes were compared with British and Australian/New Zealand B nodosus strains by use of reciprocal tube agglutination tests. These tests, as well as the cross-matching tube agglutination tests of the US serotypes, resulted in arranging the US serotypes into 11 serogroups, and comparing these serogroups with their Australian/New Zealand serogroup and British serotype counterparts. Three US serogroups and 1 additional British serotype had little or no relationship to any of the Australian/New Zealand serogroups A-H (the vaccine strains). One or more of these unrelated serogroups were found in 29% of the sources studied. The most frequently found US serotype was serotype XV at 29%. The most frequently found US serogroups were the serogroups analogous to serogroup B (43.5%) and serogroup H (37%); the other serogroups were found in 22.6% or less of the sources studied. Evaluation of 3 sources revealed that multiple serotypes in a single flock are common, multiple serotypes from a single lesion are possible, B nodosus isolates obtained from goats (unlike those from cattle) appear identical to the isolates obtained from sheep, and disease can appear in vaccinated animals, even in a flock that appears to be harboring only a single serogroup-B serotype (the serogroup for which there are 3 strains in the current vaccine).

Monoclonal antibodies against pili of serologically distinct Bacteroides nodosus.

Several monoclonal antibodies (McAbs) against pili of Bacteroides nodosus were examined to determine their reactivity with 11 different serotypes. One McAb was identified by enzyme-linked immunosorbent assay (ELISA) analysis that bound to nine of the 11 serotypes and another that bound to the remaining two serotypes tested. In addition, some McAbs demonstrated specificity for a single serotype, while others displayed specificities for up to five other serotypes. Comparison of immunoblot analysis with the ELISA revealed that the former method was not as sensitive in that all McAbs positive by the ELISA, were not positive by immunoblot. Possible explanations of these findings are discussed. There appear to be several antigenic determinants on B. nodosus pili and considerable sharing of these determinants between pili types. The 11 serotypes analyzed by the McAbs in this report are representative of all 20 US serotypes as well as the A-set and D-set categories of Australia. Therefore, the two epitopes recognized by two of the McAbs reported herein encompass all of the currently characterized B. nodosus serotypes and may provide a basis for bivalent vaccines efficacious for all types of B. nodosus induced footrot in sheep.

Diversity of pilin of serologically distinct Bacteroides nodosus.

Pili from 11 distinct serotypes of Bacteroides nodosus were examined for diversity of pilin polypeptide subunits among serotypes and for purity of the pilin preparations. The pilin of all 11 samples was shown to be homogeneous. Mean +/- SD molecular weight of the pilin of 7 serotypes (A198, IV, V, VI, IX, XVII, and XVIII) was 18,500 +/- 100. The pilin of serotypes I, III, and VIII had molecular weight of 17,600, 19,400, and 19,000, respectively. Serotype XV differed greatly from the other 10 serotypes in that 2 distinct polypeptide bands with molecular weight of approximately 7,800 and 6,200 were detected. We suggest that these 2 low molecular weight bands resulted from proteolytic cleavage of the pilin protein.

Electron microscopic study of Bacteroides nodosus pili and associated structures.

Surface structures of Bacteroides nodosus were examined by electron microscopy. Collodion film and chrome shadowing were used for maximizing the visualization of B nodosus pili and ring structures. The existence of B nodosus pili in foot rot lesions was confirmed. Contrary to previous reports, it was found that B nodosus pili production can be retained through serial broth transfer under certain conditions. Capsule production by B nodosus was irregular in that it could be either lacking or variable in thickness. A bacteriophage capable of infecting B nodosus also was detected.

Effectiveness of vaccination in controlling ovine footrot.

Efficacy of reducing footrot by use of a commercial vaccine was evaluated over 2 yr with 223 ewes from five crossbred genotypes. Ewes were assigned randomly within genotype, age and initial footrot status to a 2 x 3 factorial array of vaccination in the 1st yr and fall vaccination, winter vaccination or control in the 2nd yr. The flock contained a single Bacteroides nodosus serotype (XV) known to be highly cross-reactive with one of the vaccine serotypes (British serotype H). Vaccination reduced footrot incidence by 61% (P less than .01) in the 1st yr and by 45% (P less than .01) in the 2nd yr. Vaccination of previously uninfected ewes did not significantly reduce the rate of new infection, but vaccination of infected ewes reduced re-infection by 92% (P less than .01). Vaccination in the 1st yr failed to produce any carryover or additive protection in the 2nd yr. Genotypes differed in both footrot incidence (P less than .05) and footrot reduction following vaccination (P less than .05), but the effect was inconsistent between years. Vaccination increased serum antibody titers in both years (P less than .01). Among vaccinates in the 1st yr, infected ewes had lower titer levels than uninfected ewes (P less than .01), but no correlation between titer level and incidence was observed in the 2nd yr.

Susceptibility of Bacteroides nodosus to various antimicrobial agents.

The susceptibility of 18 strains of Bacteroides nodosus to 21 antimicrobial agents was tested in vitro. Penicillin was the most effective antibiotic tested. Other antibiotics tested, in order of relative efficacy, were cefamandole, clindamycin, tetracycline, chloramphenicol, erythromycin, sodium cefoxitin, tylosin tartrate, nitrofurazone, tinidazole, and dihydrostreptomycin sulfate. Tests of solutions of 4 antibiotics in 70% ethanol indicated that ethanol served primarily as a diluent and did not contribute substantially to the curative effect of such topical medications on foot rot lesions in sheep. Of the chemicals commonly used in foot baths for treatment of ovine foot rot, copper sulfate was most effective, followed by zinc sulfate, then formalin. Several commercial disinfectants and iodine were quite effective against B nodosus, whereas 5.25% sodium hypochlorite and 70% ethanol alone were relatively ineffective.

Serotypic and biochemical characterization of Bacteroides nodosus isolates from Oregon.

Ninety-seven Bacteroides nodosus isolates were characterized by the tube agglutination test. Fourteen serotypes were identified including isolates that were serologically similar to Australian serotypes A, B and C. One additional isolate remains untyped and possibly represents another serotype. The isolates were cultured from 20 different flocks. Multiple isolates were obtained from 15 of the flocks and 13 of these had two to seven different B. nodosus serotypes. Eleven B. nodosus isolates representing one Australian and ten Oregon serotypes were nonfermentative in various carbohydrates and did not produce indole. These isolates all exhibited proteolytic activity. The prototype strains of 12 of the 14 serotypes demonstrated virulence as assessed by an elastase production assay.

Selective medium for isolation of Bacteroides nodosus.

The sensitivity of Bacteroides nodosus, the causative agent of sheep foot rot, to 24 selected antimicrobial agents was tested. Many contaminants ordinarily associated with foot rot lesions were sensitive to lincomycin, whereas B. nodosus demonstrated resistance to this antibiotic. A concentration of 1 microgram of lincomycin per ml of basal medium optimally inhibited contaminants while allowing growth of B. nodosus. The basal medium was Eugon agar with 0.2% yeast extract and 10.0% defibrinated horse blood. Parallel inoculations of 31 foot rot lesion specimens onto basal medium and basal medium containing lincomycin (selective medium) were performed. B. nodosus was isolated from 16 of the specimens cultured on the selective medium and from only 3 of the specimens cultured on the basal medium. The concentration of agar in the standard Eugon medium was found to influence the growth of B. nodosus in the presence of lincomycin. Trimethoprim also exhibited potential selectivity for B. nodosus.